Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

August 12, 1994

Ms. Joanne B. Linhard
Organizational Resources Counselors, Inc.
1910 Sunderland Place, N.W.
Washington, D.C. 20036

Dear Ms. Linhard:

This is in response to your December 20, 1993 letter, requesting interpretation of the Control of Hazardous Energy Source (Lockout/Tagout) standard, 29 CFR 1910.147. Please accept our apology for the delay in responding. Your questions and our replies follow:

Question 1: At one location there are over 3000 different energy sources and different procedures for controlling hazardous energy. Would each machine require a specific, written procedure?

Reply: With the following exceptions, energy control procedures specified by 1910.147(c)(4) must be developed, documented and utilized for the control of potentially hazardous energy when employees are performing servicing and/or maintenance on machines or equipment:

1. The 1910.147 standard does not apply to work on cord and plug connected electrically powered equipment under the conditions specified by 1910.147(a)(2)(iii)(A).

2. Employers need not document the required energy control procedures for a particular machine or equipment when all of the elements of the note following 1910.147(c)(4)(i) exist.

3. Please note that employees interact with machines and equipment either when they are in the normal production operations mode or in the servicing and/or maintenance mode. By the Note following 1910.147(a)(2)(ii)(B), minor tool changes and adjustments and other minor servicing activities, which take place during normal production operations, are not covered by the 1910.147 standard if they are routine, repetitive, and integral to the use of the machine or equipment for production provided that the work is performed using alternative measures which provide effective protection (See 1910 Subpart O - Machine Guarding). If an employee cannot perform minor tool changes and adjustments and other minor servicing activities during normal production operations without potential exposure to hazardous energy otherwise protected either by guarding or by alternative measures providing effective protection, then the employer must effect the servicing and/or maintenance mode and comply with applicable provisions of paragraphs (c) through (f) of the lockout/tagout standard.

4. One energy control procedure may be used for similar machines and/or equipment if the procedure adequately addresses the unexpected energization hazards related to each machine.

Question 2: A group of machines and equipment which includes a brush cleaner and associated cleaner slump, a dryer, a conveyor and a stacker, collectively, have multiple, including electrical, thermal and mechanical (including pneumatic and hydraulic), energy sources. All the machines cannot be completely shut down for servicing and/or maintenance of any one of these machines or equipment. Can an individual machine or equipment, for example, the dryer, be locked out separately for servicing and/or maintenance? Also, is an energy control procedure required for each machine or equipment on which servicing and/or maintenance is to be performed?

Reply: An individual machine, for example the dryer, or individual equipment or a machine and equipment combination, such as the brush cleaner and associated cleaner slump, may be locked out by an authorized employee performing servicing and/or maintenance. Separate energy control procedures would be required, for example, for the dryer and for the brush cleaner and associated cleaner slump. These separate energy control procedures must ensure that servicing and maintenance employees are not exposed to hazards of other interconnected and nearby machines or equipment including the conveyor and stacker.

Question 3: Do the samples of a work authorization permit and of energy control procedures enclosed with my letter meet the documentation requirements of 1910.147?

Reply: A work authorization permit is not required by the 1910.147 standard. The value of this sample permit is questionable since it does not identify what work is authorized on the dryer. Also, the sample does not indicate that lockout in accordance with an established energy control procedure is a prerequisite to working on the dryer.

The sample energy control procedures are deficient. For example, there is no specific statement in the sample on the intended use of the energy control procedure as required by 1910.147(c)(4)(ii)(A). Other energy control procedures requirements are contained in 1910.147(c)(4)(ii). These requirements are delineated further, for example, 1910.147(d) covers the application of control, in the lockout/tagout standard.

Please note that the 1910.147 standard does not cover exposure to electrical hazards from work on, near or with conductors or equipment in electrical installations. Such work is covered by Subpart S - Electrical of the 1910 General Industry standards. Electrical Safety - Related Work Practices, that is, 1910.331 - 335, include lockout and tagging requirements for employees working on or near exposed deenergized parts. By note 2 following 1910.333(b)(2), lockout and tagging procedures that comply with paragraph (c) through (f) of 1910.147 will be deemed to comply with 1910.333(b)(2) provided that:

1. The procedures address the electrical safety hazards covered by Subpart S; and

2. The procedures also incorporate the requirements of paragraphs 1910.333(b)(2)(iii)(D) and (b)(2)(iv)(B).

Thank you for your interest in Occupational Safety and Health. If we may be of further assistance, please contact the Office of General Industry [at (202) 693-1850].


John B. Miles, Jr., Director Directorate of Compliance Programs